A simple data source implementation that simulates a data source with a given number of virtual records inside.
It is called empty data source because even though it has one or more records inside, all the report fields
are null for all the virtual records of the data source.

The simplest implementation of the JRDataSource
interface, this class can be used in reports that do not display data from the supplied data
source, but rather from parameters, and when only the number of virtual rows in the data
source is important.